Ridecamp: [RC] Road founder & Grass Founder. Difference?

Hi. I have a friend who's horse road foundered a couple of months ago. This is a Paso Fino. They do ride on the road but not a whole lot. Maybe it's the Paso Fino moving of the legs that did him in, you know, the pounding? I know they do have hock problems in the future.  Anyway, this horse was on grass every day, all day because the owner said road founder was different than grass founder. Well, the horse got so bad that he couldn't get up to stand anymore and they put him down. 
Is there a difference between the two? Do you have to watch the grass intake when a horse has road foundered? I say yes because founder is founder but what do I know?
Some of us friends are curious. Thanks. Deb